The present invention relates geneally to apparatus for placing insulators in magnetic core slots, whether such apparatus is of a type that is utilized primarily for inserting only insulators into the slots of a core, and/or of a type that may be used for inserting both insulators and side turn portions of windings into such slots.
There are numerous patents in the art which illustrate apparatus that may be used for placing both side turn portions of coils and insulators into slots of a magnetic core. For example, Smith et al U.S. Pat. No. 3,831,255 of Aug. 27, 1974; Lauer et al. U.S. Pat. No. 3,829,953 of Aug. 20, 1974; Smith U.S. Pat. No. 3,698,063 of Oct. 17, 1972; Arnold et al U.S. Pat. No. 3,579,818 of May 25, 1971; Hill U.S. Pat. No. 3,324,536 of June 13, 1967; and Kieffer U.S. Pat. No. 3,748,714 of July 31, 1973, all show and describe apparatus that may be utilized for this purpose. The specific location of insulators (also sometimes called wedges) in slots relative to coil side turn portions are well illustrated, for example, in Hill et al. U.S. Pat. No. 3,694,887 of Oct. 3, 1972. As best revealed in this last reference Hill et al. patent, insulation pieces in a magnetic core may typically include ground insulation (also called cell insulators); insulators that separate the side turn portions of two different winding phases; and slot closure insulators (or wedges) which lie along axially extending core slot openings adjacent the core defined by the core.
Other equipment is utilized simply for placing between phase or slot closure insulators (both of which are sometimes called wedges) in core slots. One patent that describes wedge placing alone is Peters U.S. Pat. No. 3,805,357 which issued Apr. 23, 1974. Still another approach that may be utilized when placing only insulators is taught in co-pending application Ser. No. 666,143 which was filed Mar. 11, 1976 in the name of Alan L. Kindig and Ronald H. Brown, and which application is assigned to the same assignee as the present application.
A brief review of the above-reference patents will quickly reveal that elongate members (variously called wedge pushers, pusher rods, wedge push rods, and so forth) are utilized in many of the known types of insulator placing equipment. In many of these, the insulator pushers are guided along pathways in which elongate insulator pieces are retained. The leading end of the insulator pushers engage the trailing end of the insulators and then advance the insulators axially into and along slots of a magnetic core (e.g., a dynamoelectric machine stator or rotor core).
In some of the above-referenced patents (for example, see Smith et al U.S. Pat. No. 3,831,255 or Arnold U.S. Pat. 3,579,818) elongate pushers transfer insulators downwardly into a wedge guide housing. Subsequently, other elongate pushers advance the same insulators from the wedge guide housing upwardly and axially into and along the slots of magnetic cores.
Known insulator pushers are designed so that at least the leading ends thereof are configured to have a relatively close sliding tolerance (e.g., a tolerance of about 0.003 of an inch or 0.076 mm) with passages along the wedge guide housing (or other wedge guiding structure) along which the insulators are moved. Satisfactory operation of the apparatus requires that this relatively close dimensional tolerance be maintained, because the insulators are typically formed of thin sheet material which may be only 0.014 inches (0.356 mm) thick and if the trailing portions thereof slip between the insulator guiding walls and the leading ends of the insulator pushers; the insulators will become wedged therebetween and jam the machine.
A review of the above-referenced patents (all of which are incorporated herein by reference for background information) will reveal that much of the equipment in which elongate insulator push rods are utilized is relatively complex. Moreover, jamming of one or more insulator pushers could damage other parts of the equipment, and thus be costly to repair (in terms of material, machined parts, and time). In some equipment with which we are familiar, the pushers are made of about three-sixteenths inch round music wire and have machined brass tip silver soldered to the leading end thereof. This approach leads to wear of the pusher tips but not the wedge guide surfaces; but these pushers can cost as much as $27 each.
Elongate insulator pushers (or at least parts thereof) often are formed of a material that will wear away during normal usage, or yield in the event that the mechanism becomes jammed. Then, in the event a malfunction of the equipment occurs, the insulator pushers themselves are replaced and, hopefully, the insulator guide members will not have been excessively damaged.
The above-reference patents also reveal that a relatively large number of insulator pushers are utilized in any given piece of equipment. In many cases, a number of pushers will be provided that equal the number of slots of the core that is to be placed on the machine. Thus, it is common practice to provide 24, 36, (or more) pushers in each piece of equipment.
When the pushers are manufactured by machining the trailing end of a length of music wire (so that the trailing end thereof can be mounted into the insulator placing equipment), and silver soldering a brass pusher head thereto; the pushers themselves are expensive and a substantial amount of labor expense is involved in removing broken or damaged insulator pushers and then re-assembling the equipment with a replacement insulator pusher.
In equipment with which we are familiar and wherein bronze tipped pushers are used, we have observed that failure of a pusher is usually associated with an insulator (or wedge) being "dropped"--i.e., trapped between the pusher tip and a wedge guide wall. When this occurs, the silver solder joint between the music wire push rod and bronze tip often fails when the machine attempts to return the pushers to their rest position. It then becomes necessary to spend a considerable amount of time in removing the jammed bronze tip from the apparatus, as well as the music wire pusher. We have found that the actual machine down time associated with a failure of this type may be as much as 3 hours.
Another prior approach has been to make pushers from rectangular drill rod stock which is machined to have the desired contours and shapes. The problem with this approach is that pushers made in this manner can cost as much or more than pushers made according to the music wire bronze tip approach. Moreover, failure of a machined drill rod (or other steel) pusher can result in damage to adjoining pushers, or to the wedge guide housing itself. In that event, three or more pushers may have to be replaced because of the failure of a single pusher. Yet another problem associated with the approach just described is the substantial machining and grinding operations that must be performed in order to manufacture a pusher of the overall desired shape and contour; and it is again emphasized that this is in addition to the possibility of galling and other damage to the wedge guide housing that might occur at the time of pusher failure.
We have now devised a new and improved insulator pusher, method of making the same, and method of making equipment utilizing the same so that our new and improved insulator pushers should cost only about one-tenth as much as those of the prior art. Surprisingly, when failure does occur, machine down time is reduced to only 1 and 1/2 hours because the new and improved pushers are much easier to remove and replace. In addition, failure of a pusher is now much less likely to cause damage to any other part of the machine. It is also surprising that we have now determined that use of our invention results in much less frequent pusher malfunctions and thus leads to less overall insulator pusher damage and breakage.
Accordingly, one general object of the present invention is to provide improved insulator pushers which are less susceptible to damage and wear in practice than insulator pushers of the prior art.
It is another object of the present invention to provide new and improved insulator pushers which, when jammed in a piece of equipment, are relatively easy to remove therefrom.